Plato Charmides 165

But he says it in a rather riddling fashion, as a prophet would; for Know thyself! and Be temperate! are the same, as 165a the inscription ¹ and I declare, though one is likely enough to think them different—an error into which I consider the dedicators of the later inscriptions fell when they put up ² and ³ For they supposed that was a piece of advice, and not the god’s salutation of those who were entering; and so, in order that their dedications too might equally give pieces of useful advice, they wrote these words and dedicated them. Now my object in saying all this, Socrates, is to abandon to you all the previous argument— 165b for, though perhaps it was you who were more in the right, or perhaps it was I, yet nothing at all certain emerged from our statements—and to proceed instead to satisfy you of this truth, if you do not admit it, that temperance is knowing oneself.
  Why, Critias, I said, you treat me as though I professed to know the things on which I ask questions, and needed only the will to agree with you. But the fact of the matter is rather that I join you in the inquiry, each time that a proposition is made, because I myself do not know; I wish therefore to consider first, 165c before I tell you whether I agree or not. Now, give me a moment to consider.
  Consider then, he said.
  Yes, and I am considering, I said. For if temperance is knowing anything, obviously it must be a kind of science, and a science of something, must it not?
  It is, he replied, and of itself.
  And medicine, I said, is a science of health?
  Certainly.
  Then if you should ask me, I said, wherein medicine, as a science of health, is useful to us, and what it produces, 165d I should say it is of very great benefit, since it produces health; an excellent result, if you allow so much.
  I allow it.
  And so, if you should ask me what result I take to be produced by building, as the builder’s science, I should say houses; and it would be the same with the other arts. Now it is for you, in your turn, to find an answer to a question regarding temperance—since you say it is a science of self, Critias—and to tell me what excellent result it produces for us, 165e as science of self, and what it does that is worthy of its name. Come now, tell me.
  But, Socrates, he said, you are not inquiring rightly. For in its nature it is not like the other sciences, any more than any of them is like any other; whereas you are making your inquiry as though they were alike.